Power supply apparatus and electronic device having the power supply apparatus

ABSTRACT

A power supply to improve an EMI characteristic and an electronic device having the power supply. The power supply includes a power converter to convert an alternating current (AC) power applied from outside to a direct current (DC) power, a ground portion to supply a ground power to the power converter and a noise attenuator to reduce noise by blocking a harmonic current generated by a driving of the power converter from passing through the ground portion. Accordingly, the stable ground power can be supplied to the internal elements by avoiding the potential change of the ground power and the noise caused by the flow of the harmonic current can be reduced by shortening the harmonic current path. Therefore, the EMI characteristic can be improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 (a) from KoreanPatent Application No. 10-2007-0047247, filed on May 15, 2007, in theKorean Intellectual Property Office, the disclosure of which isincorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present general inventive concept relates generally to a powersupply apparatus (power supply) and an electronic device including thepower supply. More particularly, the present general inventive conceptrelates to a power supply to avoid a potential change of a ground powerand enhancing EMI characteristic by reducing a length of a harmoniccurrent path, and an electronic device including the power supply.

2. Description of the Related Art

In general, electronic devices performing a certain function withelectronic elements, for example, image forming apparatuses for printingimage on a printing medium such as printers, copiers, multifunctionperipherals (MFP), and fax machines, receive a commercial alternatingcurrent (AC) power from outside and convert the AC to a driving power ofa potential level suitable for each electronic device. To execute presetfunctions of the electronic devices, the power supply is required forconverting the commercial AC power to the driving power.

Of the power supplies, a Switching Mode Power Supply (SMPS) is mostlyfrequently used. The SMPS switches DC power, which is obtained byrectifying and smoothing the commercial AC power input from the outside,to a certain high frequency, e.g., to a high frequency of about 100 kHzto convert to a desired voltage using a transformer in high efficiency.

Typically, the power supply such as SMPS needs a ground power togetherwith the commercial AC power to provide a ground potential to eachelement of the power supply. Accordingly, a ground part for supplyingthe ground power is included in the power supply.

The layout pattern of the ground part is formed as large as possible toensure a stable potential level of the ground power, that is, to preventa change of the potential level of the ground power. To supply thestable ground power to the internal elements, the internal elements arecommonly grounded to the ground part as constructed above.

However, when the commercial AC power of a sine wave is applied to theinternal elements of the electronic device, every internal devicethrough which the current flows acts as the source of harmonic current.As the internal devices are commonly grounded to the ground part, thecurrent path of the harmonic current is lengthened. Accordingly, a longcurrent path may increase noise components and noise problems. The noiseincrease may cause deterioration of an electromagnetic interference(EMI) characteristic of the power supply.

Therefore, to avoid the degradation of the EMI characteristic, what isneeded is a method to reduce a harmonic current path and to maintain astable potential of the ground power.

SUMMARY OF THE INVENTION

The present general inventive concept provides a power supply to supplya stable ground power by preventing a potential change of the groundpower and to enhance an EMI characteristic by reducing the harmoniccurrent path.

The present general inventive concept also provides an electronic deviceincluding the power supply.

Additional aspects and utilities of the present general inventiveconcept will be set forth in part in the description which follows and,in part, will be obvious from the description, or may be learned bypractice of the general inventive concept.

The foregoing and/or other aspects and utilities of the generalinventive concept may also be achieved by providing a power supplyapparatus that includes a power converter to convert an alternatingcurrent (AC) power applied from outside to a direct current (DC) power,a ground portion to supply a ground power to the power converter and anoise attenuator to reduce noise by blocking a harmonic currentgenerated by a driving of the power converter from passing through theground portion.

The noise attenuator may have an inductance component.

The noise attenuator may be a bead.

The noise attenuator may be integrally formed with the ground portion.

The noise attenuator may be formed in a maximum resistance area in aregion of the ground portion.

The ground portion may include a multilayered structure including aplurality of substrates. The noise attenuator may be formed in a jumperarea to connect the ground portion on the substrates.

The ground portion may have a layout including a substrate and aconnection line, and the noise attenuator may be formed in at least oneof a place where a distance between one connection line and an otherconnection line relatively decreases and a place where a cross-sectionof the connection line relatively decreases.

The power converter may include a first rectifier/smoother circuit toconvert the AC power to a first DC power, a pulse generator driven bythe first DC power to generate a pulse signal of a preset period, atransformer driven by the pulse signal to convert the first DC power toa second AC power of a preset level and a second rectifier/smoothercircuit to convert the second AC power to the second DC power.

The pulse generator may be a pulse width modulator (PWM).

The foregoing and/or other aspects and utilities of the generalinventive concept may also be achieved by providing an electronic deviceincludes a power supply apparatus to convert I AC power applied fromoutside to a driving power and output the driving power, and anoperating portion including at least one internal element which isdriven by the output driving power, to perform a preset function. Thepower supply apparatus includes a power converter to convert the ACpower to the driving power, a ground portion to supply a ground power tothe power converter, and a noise attenuator to reduce noise by blockinga harmonic current generated by the driving of the power converter frompassing through the ground portion.

The noise attenuator may have an inductance component.

The noise attenuator may be a bead.

The noise attenuator may be integrally formed with the ground portion.

The noise attenuator may be formed in a maximum resistance area in aregion of the ground portion.

The ground portion may include a multilayered structure including aplurality of substrates. The noise attenuator may be formed in a jumperarea for connecting the ground portion in the substrates.

The ground portion may have a layout including a substrate and aconnection line. The noise attenuator may be formed in at least one of aplace where a distance between one connection line and an otherconnection line relatively decreases and a place where a cross-sectionof the connection line relatively decreases.

The operating portion may be an image forming apparatus which is drivenby the driving power to print image data on a recording medium.

The power converter may include a first rectifier/smoother circuit toconvert the AC power to a first DC power, a pulse generator driven bythe first DC power to generate a pulse signal of a preset period, atransformer driven by the pulse signal to convert the first DC power toa second AC power of a preset level and a second rectifier/smoothercircuit to convert the second AC power to the second DC power.

The stable ground power can be supplied to the internal elements byavoiding the potential change of the ground power and the noise causedby the flow of the harmonic current can be reduced by shortening theharmonic current path. Therefore, the EMI characteristic can beimproved.

The foregoing and/or other aspects and utilities of the generalinventive concept may also be achieved by providing a power supplyapparatus including a ground portion to provide ground power and a noiseattenuator unit disposed at a maximum resistance portion of the groundportion to reduce a harmonic current path through the ground portion andto maintain a stable potential of the ground power.

The foregoing and/or other aspects and utilities of the generalinventive concept may also be achieved by providing a method ofsupplying power the method including converting alternating current (AC)power applied from outside to direct current (DC) power by a powerconverter, supplying ground power to the power converter by a groundportion and reducing noise by blocking harmonic current generated bydriving of the power converter from passing through the ground portionby a noise attenuator.

The foregoing and/or other aspects and utilities of the generalinventive concept may also be achieved by providing a computer-readablerecording medium having embodied thereon a computer program to execute amethod, wherein the method includes converting alternating current (AC)power applied from outside to direct current (DC) power by a powerconverter, supplying ground power to the power converter by a groundportion and reducing noise by blocking harmonic current generated bydriving of the power converter from passing through the ground portionby a noise attenuator.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and utilities of the present generalinventive concept will become apparent and more readily appreciated fromthe following description of exemplary embodiments, taken in conjunctionwith the accompanying drawings of which:

FIG. 1 is a simplified diagram illustrating a power supply according toan exemplary embodiment of the present general inventive concept;

FIG. 2 is a detailed diagram illustrating the power supply according toan exemplary embodiment of the present general inventive concept;

FIG. 3 is a detailed circuit diagram illustrating the power supply ofFIG. 2;

FIG. 4 is a graph of a waveform illustrating EMI generation according toa driving of the power supply of FIG. 3;

FIGS. 5, 6 and 7 are graphs of a waveform illustrating the EMIgeneration according to a driving of a power supply constructeddifferently from the power supply according to an exemplary embodimentof the present general inventive concept;

FIG. 8 is a diagram illustrating an additional function of the powersupply according to an exemplary embodiment of the present generalinventive concept;

FIG. 9 is a simplified diagram illustrating an electronic deviceaccording to an exemplary embodiment of the present general inventiveconcept; and

FIG. 10 is a flowchart illustrating a method of supplying poweraccording to an exemplary embodiment of the present general inventiveconcept.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to embodiments of the presentgeneral inventive concept, examples of which are illustrated in theaccompanying drawings, wherein like reference numerals refer to the likeelements throughout. The embodiments are described below in order toexplain the present general inventive concept by referring to thefigures.

FIG. 1 is a simplified diagram illustrating a power supply according toan exemplary embodiment of the present general inventive concept.

The power supply 100 of FIG. 1 includes a power converter 200, a groundportion 300, and a noise attenuator 400.

The power converter 200 receives a commercial alternating current (AC)power AC_IN from outside, converts the AC power to a direct current (DC)power of a certain potential level, and outputs DC_OUT. The powerconverter 200 includes signal converting elements therein, for example,elements such as a transformer, inverter, and rectifier. The internalelements convert and flow the sine AC power and thus serve as a sourceof generating a harmonic current H_current.

The harmonic current H_current generated at the power converter 200flows through the ground portion 300 connected to each element.

The ground portion 300 supplies a ground voltage within an acceptableerror range, for example, the ground voltage of 0V to the internalelements of the power converter 200. The ground portion 300 is laid outin a pattern as wide as possible over a circumference or a preset areaof a substrate of the power supply 100. The shape of the ground portion300 may vary according to a different layout pattern of the differentpower supply 100.

The harmonic current H_current generating from the driving of the powerconverter 200 passes through the ground portion 300. Theoretically,since the ground portion 300 has the certain potential level, even whenthe harmonic current H_current is fed to the ground portion 300, it doesnot flow through the ground portion 300. In practice, as the differentground voltage GND is generated in every area of the ground portion 300according to the layout pattern of the ground portion 300, the harmoniccurrent H_current passes based on the potential difference of the groundportion 300.

For instance, in the layout, the ground portion 300 can be formed in awider pattern with a smaller resistance along adjacent circuit patternsor in a narrow pattern with a greater resistance. When the groundportion 300 is formed as above, the area of the ground portion 300having the greater resistance becomes high potential and the area of theground portion 300 having the smaller resistance becomes low potential.Thus, the potential difference is produced and the harmonic currentH_current passes through the ground portion 300.

The resistance of the ground portion 300 may vary according to aproximity to the adjacent circuit patterns. In an exemplary embodiment,the noise attenuator 400 is formed at a maximum resistance area of theground portion 300. For example, when the ground portion 300 is laid outwith a substrate and at least one connection line, a jumper area can beprovided to each connection line. The jumper area is an area where oneconnection line jumps an other connection line at an intersection pointof the two connection lines not to contact each other. To provide thejumper area to each connection line, the ground portion 300 and thenoise attenuator 400 can be implemented using a circuit of the layeredstructure where a plurality of substrates or a plurality of layers isdeposited. Thus, the resistance in the jumper area differs from theresistance of the other areas, and the potential difference caused bythe resistance difference makes the harmonic current H_current passthrough.

The noise attenuator 400 is connected to the ground portion 300 to blockthe path of the harmonic current H_current. In more detail, when theH_current is caused by the potential difference as mentioned above, thenoise attenuator 400 is formed in a certain area of the ground portion300 to shorten the harmonic current path passing through the groundportion 300.

For example, the noise attenuator 400 can be formed in the area of themaximum resistance among the areas of the variable resistance asdescribed earlier.

Thus, the path of the harmonic current H_current flowing through theground portion 300 is blocked by the noise attenuator 400 and thusshortened. As a result, the noise, which increases as the path increasesby the resistance component of the harmonic current path, can bemitigated. This noise mitigation prevents the EMI characteristicdegradation caused by the noise.

The power supply 100 is now explained in further detail.

FIG. 2 is a detailed diagram of the power supply 100 according to anexemplary embodiment of the present general inventive concept, and FIG.3 is a detailed circuit diagram of the power supply 100 of FIG. 2.

The power supply 100 of FIG. 2 includes the power converter 200, theground portion 300, and the noise attenuator 400.

The power converter 200 includes a first rectifier/smoother circuit 220,a pulse generator 240, a transformer 260, and a secondrectifier/smoother circuit 280.

The first rectifier/smoother circuit 220 includes a rectifier element222 (FIG. 3) and a smoother element 224 (FIG. 3) to receive and rectifya first AC power AC1 from an AC power input portion 120 which receivesthe commercial AC power AC_IN from the outside, smooth the rectifiedpower, and generate and output a first DC power DC1.

The AC power input portion 120 to output the first AC power AC1 to thefirst rectifier/smoother circuit 220 is now described. As illustrated inFIG. 3, the AC power input portion 120 includes elements of a fuse 122,a varistor 124, and an arrester 126 to protect the power supply 100 whena potential level of the input AC power is greater than a presetpotential level. The AC power input portion 120 also includes an LCfilter 128 to remove the noise component from the input AC power.

The pulse generator 240 includes a switching element TR2, a snubbercircuit 242, a pulse width modulator (PWM) IC 244, and an output voltagecontroller 246.

The snubber circuit 242 prevents switching loss caused by an overshootor undershoot noise by counter electromotive force generated from anon/off operation of the switching element TR2.

The PWM IC 244 operates upon receiving a first DC power DC1 from thefirst rectifier/smoother circuit 220, generates a control signal fed toa gate of the switching element TR2, that is, a PWM signal to controlthe first DC power DC1 applied to the transformer 260 by switching to ahigh frequency of about 100 kHz, and outputs the PWM signal to theswitching element TR2. The PWM IC 244 may employ a controller.

Since the PWM control scheme is used to control a duty ratio of theswitching signal in this embodiment of the present general inventiveconcept, the PWM signal is generated by the PWM IC. It should beunderstood that proper ICs can be constituted respectively when afrequency control scheme to control a frequency of the switching pulseand a phase control scheme to control a phase of the switching pulse areused.

For example, the switching element TR2 can be constituted using a PNPtransistor. The switching element TR2 controls the first DC power DC1applied to a primary coil of the transformer 260 by switching on and offaccording to the PWM signal of the controlled duty ratio output from thePWM IC 244.

The output voltage controller 246 includes a light receiving element PC1of a photocoupler which operates on and off based on a light from alight emitting element (not illustrated) of the photocoupler emittingaccording to power output through a second rectifier/smoother circuit280, to control the PWM IC 244 to regulate the duty ratio according tothe potential level of the output voltage DC2 n (FIG. 2).

The output voltage controller 246 can include a comparator circuit (notillustrated) to which a reference power and the output power areapplied, to output the control signal to the PWM IC 244 according to thelevel difference of the reference power and the output power.

A DC power receiving portion 248 in FIG. 3 is provided to receive the DCpower from the transformer 260 which directly generates and supplies theDC power having the potential level different from the first DC powerDC1 operating the PWM IC 244.

Referring to FIGS. 2 and 3, the transformer 260 can include the primarycoil and at least one secondary coil facing the primary coil to convertthe first DC power DC1 to the second AC power AC2 with the presetpotential level based on a ratio of a number of turns of the primarycoil and the secondary coil.

The second rectifier/smoother circuit 280 receives and rectifies thesecond AC power AC2 induced to the secondary coil of the transformer260, generates and outputs the second DC power DC2 n by smoothing therectified power.

The second coil of the transformer 260 can include a plurality ofsecondary coils to generate a plurality of potential levels of differentpotential levels, for example, to generate the DC power of 5V or 24V,and the second rectifier/smoother circuit 280 can include rectifierelements D2 and D6 and smoother elements C4 and C11 connected to thecoils as illustrated in FIG. 3.

While the DC powers are illustrated using the different referencenumerals in FIGS. 2 and 3, the second DC power DC2 n of FIG. 2 denotesthat the DC power can be output with the different levels, and coverboth the second DC powers DC_OUT1 and DC_OUT2 of FIG. 3.

The ground portion 300 supplies the ground voltage within an acceptableerror range, for example, the ground voltage of 0V to the internalelements of the power converter 200. While the ground portion 300illustrated as being formed in each element of the power converter 200in the circuit diagram of FIG. 3, the pattern can be formed in acircumference or the preset area of the circuit board and the elementsare commonly grounded in the actual layout.

The noise attenuator 400 is connected to the ground portion 300 to blockthe flow path of the harmonic current H_current. When the harmoniccurrent H_current is generated from the potential difference asdescribed earlier, the noise attenuator 400 is formed in a certain areaof the ground portion 300 to shorten the harmonic current path passingthrough the ground portion 300.

Accordingly, the noise attenuator 400 is connected to the ground portion300 in the pattern area of the ground portion 300 as illustrated in FIG.3, particularly, in the area of the maximum resistance among the areasof the variable resistance as illustrated in FIG. 1.

While the noise attenuator 400 is an inductor in FIG. 3, it can beformed using any circuit element having an inductance component and itstype is not limited. For example, the noise attenuator 400 can be formedusing a bead.

The noise attenuator 400 is constituted using the inductor or the beadbecause the inductance component passes the DC but not the harmonic ACH_current. Hence, the flow path of the unnecessary harmonic current canbe blocked.

Therefore, the flow path of the harmonic current H_current passingthrough the ground portion 300 can be blocked by the noise attenuator400 to shorten the harmonic current path. As a result, the noise, whichincreases as the path increases by the resistance component of theharmonic current path, is reduced. Accordingly, the degradation of theEMI characteristic caused by the noise can be prevented.

With the noise attenuator 400 formed in the power supply 100, the EMIgeneration information according to the driving of the power supply 100is compared with examples.

FIG. 4 is a graph of a waveform illustrating EMI generation when thepower supply according to an exemplary embodiment of the present generalinventive concept is used, and FIGS. 5, 6 and 7 are graphs of thewaveform illustrating the EMI generation according to the driving of apower supply constructed differently from the power supply according toan exemplary embodiment of the present general inventive concept.

Particularly, FIG. 5 illustrates an EMI generation waveform when thenoise attenuator 400 is removed from the power supply of FIG. 3, FIG. 6illustrates the EMI generation waveform when the noise attenuator 400 isconnected to the second rectifier/smoother circuit 280 in the powersupply of FIG. 3, and FIG. 7 illustrates the EMI generation waveformaccording to the driving of the power supply when the resistance isgenerated at the non-optimal position, that is, at the non-maximumposition.

As illustrated in FIGS. 4 through 7, according to a measurement, whenthe noise attenuator 400 is formed at the optimal position; that is, atthe position of the maximum resistance as in the exemplary embodiment ofthe present general inventive concept, the EMI dB value lies within thefrequency limitation (the dB value indicated by the thick solid line inthe graphs). By contrast, when the noise attenuator 400 is not employed,the EMI dB value exceeds the limitation in the frequency band around 100MHz and thus the EMI characteristic degrades as illustrated in FIG. 5.

When the noise attenuator 400 is formed in an output stage of the ACpower, rather than an input stage, the EMI characteristic is notimproved as illustrated in FIG. 6. When the noise attenuator 400 isformed at the non-optimal position, the EMI characteristic is slightlyimproved as illustrated in FIG. 7.

FIG. 8 is a diagram illustrating an additional function of the powersupply according to an exemplary embodiment of the present generalinventive concept.

Referring now to FIGS. 3 and 8, when the noise attenuator 400 having theinductance component is formed together with the power supply 100, thecircuit patterns adjacent to the pattern of the ground portion 300 canbe considered as the electrodes facing each other, and the parasiticcapacitance exists between the circuit patterns adjacent to the groundportion 300 because the area therebetween can be considered as adielectric. Since the noise attenuator 400 has the inductance component,a parallel LC filter can be formed by the parasitic capacitance and theinductance as illustrated in FIG. 8.

Accordingly, when the noise attenuator 400 is connected to the groundportion 300 as in the exemplary embodiment of the present generalinventive concept, EMI radiation can be filtered by the parallel LCfilter formed.

FIG. 9 is a simplified diagram illustrating an electronic deviceaccording to an exemplary embodiment of the present general inventiveconcept. To explain the electronic device in detail, an image formingapparatus such as a printer is used by way of example. It should beunderstood that the power supply 100 of FIGS. 1, 2, and 3 is applicableto any apparatus which converts AC power and supplies the convertedpower to internal circuit elements.

An electronic device such as an image forming apparatus 1000 of FIG. 9includes a power supply 100, a printing controller 500, a printingengine 600, and a user interface (UI) 700.

The power supply 100 is constructed substantially the same as the powersupply 100 of FIGS. 1, 2 and 3. Hence, the power supply 100 uses thesame reference numeral. The power supply 100 has been described indetail above and shall not be explained further.

The printing controller 500 is driven by the first DC power DC_OUT2output from the power supply 100 to receive printing data from a hostdevice such as a computer and convert the received printing data to abitmap image. The printing controller 500 controls an overall operationof the image forming apparatus 1000 by outputting a control signal CS1to control the PWM IC 244 of the power supply 100 and outputting acontrol signal CS2 to control the components of the printing engine 600.

That is, the printing controller 500 controls the overall operation ofthe printing engine 600 to load and deliver a printing medium, form thebitmap image on the printing medium, fix the formed image, and dischargethe printed printing medium, and controls the overall operation of theimage forming apparatus 1000 to determine a printing error such as apaper jam during a printing job.

For instance, if the image forming apparatus 1000 is a laser printer,the printing engine 600 can include a fixing portion including anorganophotoconductor (OPC) drum, a developer, and a fixer, and a laserscanning unit (LSU) for emitting the laser beam on the OPC drum.

Each component of the printing engine 600 is driven by the second DCpower DC_OUT2 output from the power supply 100 and the control signalCS2 output from the printing controller 500, to form the bitmap imageconverted at the printing controller 500 on the printing medium as acertain image.

The UI 700 displays a driving status of the image forming apparatus 1000to a user or provides control signals input from the user to theprinting controller 500 under the control of the printing controller500.

In an exemplary embodiment of the present general inventive concept, anoperating portion can include the printing controller 500, the printingengine 600, and the UI 700 of the image forming apparatus 1000. Inanother embodiment, the operating portion can include one or morecomponents to substantially perform a preset function of an electronicdevice.

FIG. 10 is a flowchart illustrating a method of supplying poweraccording to an exemplary embodiment of the present general inventiveconcept. Referring to FIG. 10, in 1010, alternating current (AC) powerapplied from outside is converted to direct current (DC) power by apower converter. In 1020, ground power is supplied to the powerconverter by a ground portion. In 1030, noise is reduced by blockingharmonic current generated by driving of the power converter frompassing through the ground portion by a noise attenuator.

The present general inventive concept can also be embodied ascomputer-readable codes on a computer-readable medium. Thecomputer-readable medium can include a computer-readable recordingmedium and a computer-readable transmission medium. Thecomputer-readable recording medium is any data storage device that canstore data that can be thereafter read by a computer system. Examples ofthe computer-readable recording medium include read-only memory (ROM),random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, andoptical data storage devices. The computer-readable recording medium canalso be distributed over network coupled computer systems so that thecomputer-readable code is stored and executed in a distributed fashion.The computer-readable transmission medium can transmit carrier waves orsignals (e.g., wired or wireless data transmission through theInternet). Also, functional programs, codes, and code segments toaccomplish the present general inventive concept can be easily construedby programmers skilled in the art to which the present general inventiveconcept pertains.

As set forth above, the elements of the power supply are commonlygrounded to the ground portion to thus stably ensure the potential ofthe ground power of the elements.

By shortening the path of the harmonic current caused by the driving ofthe components, the noise from the harmonic current flow can be reduced.

Therefore, the EMI characteristic can be improved by suppressing the EMIradiation.

Although various embodiments of the present general inventive concepthave been illustrated and described, it will be appreciated by thoseskilled in the art that changes may be made in these embodiments withoutdeparting from the principles and spirit of the general inventiveconcept, the scope of which is defined in the appended claims and theirequivalents.

1. A power supply apparatus, comprising: a power converter to convert alternating current (AC) power applied from outside to direct current (DC) power; a ground portion to supply ground power to the power converter; and a noise attenuator to reduce noise by blocking a harmonic current generated by a driving of the power converter from passing through the ground portion.
 2. The power supply of claim 1, wherein the noise attenuator comprises: an inductance component.
 3. The power supply of claim 2, wherein the noise attenuator comprises: a bead.
 4. The power supply of claim 1, wherein the noise attenuator is connected to the ground portion.
 5. The power supply of claim 1, wherein the noise attenuator is formed in a maximum resistance area in a region of the ground portion.
 6. The power supply of claim 5, wherein the ground portion comprises: a layout including a substrate and at least one connection line; and the noise attenuator is formed in a jumper area to prevent one connection line from contacting with an other connection line.
 7. The power supply of claim 5, wherein the ground portion comprises: a layout including a substrate and a connection line; and the noise attenuator is formed in at least one of a place where a distance between one connection line and the other connection line relatively decreases and a place where a cross-section of the connection line relatively decreases.
 8. The power supply of claim 1, wherein the power converter comprises: a first rectifier/smoother circuit to convert the AC power to a first DC power; a pulse generator driven by the first DC power to generate a pulse signal of a preset period; a transformer driven by the pulse signal to convert the first DC power to a second AC power of a preset level; and a second rectifier/smoother circuit to convert the second AC power to the second DC power.
 9. The power supply of claim 8, wherein the pulse generator is a pulse width modulator (PWM).
 10. An electronic device, comprising: a power supply to convert AC power applied from outside to a driving power and output the driving power; and an operating portion including at least one internal element which is driven by the output driving power, to perform a preset function, wherein the power supply apparatus comprises: a power converter to convert the AC power to the driving power; a ground portion to supply a ground power to the power converter; and a noise attenuator to reduce noise by blocking a harmonic current generated by the driving of the power converter from passing through the ground portion.
 11. The electronic device of claim 10, wherein the noise attenuator comprises: an inductance component.
 12. The electronic device of claim 11, wherein the noise attenuator comprises: a bead.
 13. The electronic device of claim 10, wherein the noise attenuator is connected to the ground portion.
 14. The electronic device of claim 10, wherein the noise attenuator is formed in a maximum resistance area in a region of the ground portion.
 15. The electronic device of claim 14, wherein the ground portion comprises: a layout including a substrate and at least one connection line; and the noise attenuator is formed in a jumper area to prevent one connection line from contacting with an other connection line.
 16. The electronic device of claim 14, wherein the ground portion comprises: a layout including a substrate and a connection line; and the noise attenuator is formed in at least one of a place where a distance between one connection line and the other connection line relatively decreases and a place where a cross-section of the connection line relatively decreases.
 17. The electronic device of claim 10, wherein the operating portion comprises: an image forming apparatus which is driven by the driving power to print image data on a recording medium.
 18. The electronic device of claim 10, wherein the power converter comprises: a first rectifier/smoother circuit to convert the AC power to a first DC power; a pulse generator driven by the first DC power to generate a pulse signal of a preset period; a transformer driven by the pulse signal to convert the first DC power to a second AC power of a preset level; and a second rectifier/smoother circuit to convert the second AC power to the second DC power.
 19. A power supply apparatus, comprising: a plurality of components; a ground portion to provide a common ground for the plurality of components; and a noise attenuator connected to the ground portion to reduce noise by blocking a harmonic current passing through the ground portion.
 20. A power supply apparatus, comprising: a ground portion to provide ground power; and a noise attenuator unit disposed at a maximum resistance portion of the ground portion to reduce a harmonic current path through the ground portion and to maintain a stable potential of the ground power.
 21. The apparatus of claim 20, wherein the noise attenuator unit comprises: at least one of an inductor and a bead.
 22. The apparatus of claim 20, wherein the noise attenuator unit prevents an electromagnetic interference (EMI) dB value from exceeding 100 Mhz.
 23. A method of supplying power, the method comprising: converting alternating current (AC) power applied from outside to direct current (DC) power by a power converter; supplying ground power to the power converter by a ground portion; and reducing noise by blocking harmonic current generated by driving of the power converter from passing through the ground portion by a noise attenuator. 